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Kamata, Kento*; Nara, Yoshitaka*; Matsui, Hiroya; Ozaki, Yusuke
Dai-15-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (Internet), p.205 - 209, 2021/01
When considering the projects such as radioactive waste disposal, it is important to evaluate the confinement performance of underground substances in rock mass. However, the change in permeability of macro-fractured mudstone has not been sufficiently studied. Therefore, in this study, we investigated its effect on permeability by introducing a macro-fracture into a cylindrical specimen of mudstone distributed in the Horonobe area, Hokkaido. First, the hydraulic conductivity was measured by subjecting a specimen with a macro-fracture introduced by a brazilian test to a falling head permeability test. After that, it was compared with the hydraulic conductivity of the intact specimen measured by the transient pulse method. As a result, it was confirmed that the hydraulic conductivity was increased by about one order due to the introduction of macro-fracture. The increase rate of hydraulic conductivity obtained from the results of this research was smaller than that of previous researches using granite and basalt.
Kamata, Kento*; Nara, Yoshitaka*; Fujii, Hirokazu*; Zhao, Y.*; Matsui, Hiroya; Ozaki, Yusuke
no journal, ,
The precipitation of carbonate minerals in rock is expected to close the fracture opening. In Horonobe URL, we perform the carbonated water injection test to heal the EDZ by the carbonate mineral precipitation. We compare the permeability before and after the injection to evaluate the closure of fractures in the EDZ. The significant change in permeability is not recognized at the present due to the short injection period and continuous injection would be required to change the permeability of EDZ by the precipitation.
Kamata, Kento*; Nara, Yoshitaka*; Matsui, Hiroya; Ozaki, Yusuke; Fujii, Hirokazu*; Zhao, Y.*
no journal, ,
In this study, we perform a carbonated water injection experiment into the fractured rock to investigate the reduction of permeability due to the sealing of fractures by the precipitation of carbonated minerals at the 350m stage in Horonobe URL. We drilled a 80cm borehole from the drift wall and injected the carbonated water into the fractures there in the excavated damaged zone. The hydraulic test that we performed regularly during the injection experiment indicates the reduction of hydraulic conductivity slightly. To understand the mechanism of the reduction of permeability, we plan to analyze the core sample collected by overcoring.
Kamata, Kento*; Nara, Yoshitaka*; Kashiwaya, Koki*; Tada, Yohei*; Fujii, Hirokazu*; Zhao, Y.*; Matsui, Hiroya; Ozaki, Yusuke
no journal, ,
We conducted a carbonated water injection experiment at 350m stage in Horonobe URL. Two boreholes with 1m were drilled from drift wall and carbonated water was injected. The cement material powder was added one of the boreholes. The hydraulic conductivity around the borehole where only carbonated water was injected slightly decreased. The hydraulic conductivity around the borehole where both cement material powder and carbonated water decreased and increased because of the clogging of fracture by the powder and dissipation of it.